In various industrial fields, such as healthcare, welfare, robotics and electronics, there is a demand for a soft actuator having creature-like, flexible motional properties for reasons of compatibility with humans. Among other things, active research and development is being made on an actuator which uses a polymeric material and is caused to change in shape by an electrical stimulus, for reasons of controllability according to an electrical signal and possibility of being able to increase the amount of generative force per weight and volume.
The fundamental structure of these polymer actuators is such that an ionic substance is held between electronic conductors (electrodes). The actuators are known to make a bending motion and/or a stretching motion as devices, in response to voltage application across the electrodes, due to a volumetric change, an electrostatic repulsive force or the like resulting from interelectrode attractive force or ionic migration.
In particular, an actuator using a gelatinous material including carbon nanotubes (CNTs) and an ionic liquid which is a nonvolatile ion-conducting material operates at a voltage as low as several volts. In addition, the actuator is known to have excellent properties, such as exhibiting extremely high stability in the air and in a vacuum (Japanese Patent Application Laid-Open No. 2005-176428).
The above-described actuator has a configuration in which an electrolyte layer formed by gelling an ionic liquid and a polymer is held between electrode layers formed of CNTs, an ionic liquid and a polymer.
In the conventional example described in the above-mentioned Patent Document 1, however, an electrolyte layer and electrode layers are filmy membranes fabricated by a casting method or the like. Accordingly, the mobility of ions within the actuator cannot be said to be sufficiently high. Since a low efficiency of ionic migration may lead to a reduction in displacement or generative force required of an actuator, there has been the need to cope with these problems.
In addition, use of such a filmy membrane makes it difficult to arbitrarily design the balance of the actuator between the displacement and generative force thereof by methods other than changing a membrane thickness.